-tip testing found the following boot crash on a 64-bit x86 system:

[    0.405247] initcall spawn_softlockup_task+0x0/0xa5 returned 0 after 0 usecs
[    0.410004] calling  relay_init+0x0/0x40 @ 1
[    0.420005] initcall relay_init+0x0/0x40 returned 0 after 0 usecs
[    0.426355] lockdep: fixing up alternatives.
[    0.430110] Booting processor 1 APIC 0x1 ip 0x6000
[    0.030000] Initializing CPU#1
[    0.030000] masked ExtINT on CPU#1
[    0.520060] BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
[    0.530000] IP: [<ffffffff81071317>] queue_work_on+0x27/0x70
[    0.530000] PGD 0 
[    0.530000] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC
[    0.530000] last sysfs file: 
[    0.530000] CPU 0 
[    0.530000] Modules linked in:
[    0.530000] Pid: 1, comm: swapper Not tainted 2.6.31-rc8-tip #1613         
[    0.530000] RIP: 0010:[<ffffffff81071317>]  [<ffffffff81071317>] queue_work_on+0x27/0x70
[    0.530000] RSP: 0018:ffff880009007d40  EFLAGS: 00010246
[    0.530000] RAX: 0000000000000000 RBX: ffffffff81e1d0c0 RCX: 0000000000000000
[    0.530000] RDX: ffffffff824a1fa0 RSI: 0000000000000000 RDI: 0000000000000000
[    0.530000] RBP: ffff880009007d50 R08: 0000000000000000 R09: 0000000000000000
[    0.530000] R10: 0000000000000001 R11: 0000000000000001 R12: 0000000025cb39a8
[    0.530000] R13: ffffffff824a0c40 R14: ffff880009007e50 R15: 0000000000000100
[    0.530000] FS:  0000000000000000(0000) GS:ffff880009004000(0000) knlGS:0000000000000000
[    0.530000] CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
[    0.530000] CR2: 0000000000000020 CR3: 0000000001001000 CR4: 00000000000006b0
[    0.530000] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[    0.530000] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[    0.530000] Process swapper (pid: 1, threadinfo ffff88003f0da000, task ffff88003f0e0000)
[    0.530000] Stack:
[    0.530000]  ffffffff824a0c40 00000000b4b7426a ffff880009007d70 ffffffff8107157d
[    0.530000] <0> ffffffff81083846 00000000b4b7426a ffff880009007d90 ffffffff810715c9
[    0.530000] <0> 0000000000000000 00000000b4b7426a ffff880009007dc0 ffffffff81083927
[    0.530000] Call Trace:
[    0.530000]  <IRQ> 
[    0.530000]  [<ffffffff8107157d>] queue_work+0x2d/0x50
[    0.530000]  [<ffffffff81083846>] ? clocksource_watchdog+0x26/0x240
[    0.530000]  [<ffffffff810715c9>] schedule_work+0x29/0x50
[    0.530000]  [<ffffffff81083927>] clocksource_watchdog+0x107/0x240
[    0.530000]  [<ffffffff81065eee>] run_timer_softirq+0x21e/0x380
[    0.530000]  [<ffffffff81065e29>] ? run_timer_softirq+0x159/0x380
[    0.530000]  [<ffffffff81083820>] ? clocksource_watchdog+0x0/0x240
[    0.530000]  [<ffffffff810600aa>] __do_softirq+0x10a/0x200
[    0.530000]  [<ffffffff8100cb1c>] call_softirq+0x1c/0x90
[    0.530000]  [<ffffffff8100e955>] do_softirq+0x95/0xc0
[    0.530000]  [<ffffffff8105f4c5>] irq_exit+0x75/0x90
[    0.530000]  [<ffffffff81029c20>] smp_apic_timer_interrupt+0x80/0xd0
[    0.530000]  [<ffffffff8100c4f3>] apic_timer_interrupt+0x13/0x20
[    0.530000]  <EOI> 
[    0.530000]  [<ffffffff812ff997>] ? delay_tsc+0x47/0x80
[    0.530000]  [<ffffffff812ffab4>] ? __const_udelay+0x64/0x80
[    0.530000]  [<ffffffff818b3fff>] ? do_boot_cpu+0x498/0x6b3
[    0.530000]  [<ffffffff818b4567>] ? do_fork_idle+0x0/0x56
[    0.530000]  [<ffffffff810468d2>] ? complete+0x32/0x80
[    0.530000]  [<ffffffff818b4375>] ? native_cpu_up+0x15b/0x208
[    0.530000]  [<ffffffff818b69d8>] ? _cpu_up+0xf3/0x1a4
[    0.530000]  [<ffffffff818b6b4d>] ? cpu_up+0xc4/0xd7
[    0.530000]  [<ffffffff821d3f97>] ? smp_init+0x118/0x126
[    0.530000]  [<ffffffff821d40c7>] ? kernel_init+0x82/0xec
[    0.530000]  [<ffffffff8100ca1a>] ? child_rip+0xa/0x20
[    0.530000]  [<ffffffff8100c3bc>] ? restore_args+0x0/0x30
[    0.530000]  [<ffffffff821d4045>] ? kernel_init+0x0/0xec
[    0.530000]  [<ffffffff8100ca10>] ? child_rip+0x0/0x20
[    0.530000] Code: ff 0f 1f 00 55 41 89 f8 48 89 e5 48 83 ec 10 65 48 8b 04 25 28 00 00 00 48 89 45 f8 31 c0 f0 0f ba 2a 00 19 c0 31 c9 85 c0 75 2a <44> 8b 4e 20 48 8b 3e 48 89 d6 45 85 c9 44 0f 45 05 b4 f4 f7 00 
[    0.530000] RIP  [<ffffffff81071317>] queue_work_on+0x27/0x70
[    0.530000]  RSP <ffff880009007d40>
[    0.530000] CR2: 0000000000000020
[    0.530006] ---[ end trace a7919e7f17c0a725 ]---
[    0.540001] Kernel panic - not syncing: Fatal exception in interrupt

Config and full bootlog attached.

Note, i have other systems that do not trigger this crash, so it's 
something specific to this one. It has an hpet for example:

[    0.000000] ACPI: HPET 000000003fef7e90 00038 (v01 INTEL  D975XBX  000004B9 MSFT 01000013)
[    0.000000] ACPI: HPET id: 0x8086a201 base: 0xfed00000
[    0.000000] hpet clockevent registered

i tried to bisect it but it's inconclusive:

 # bad:  [32beef9c] Merge branch 'perfcounters/core'
 # bad:  [b6413360] manual merge of x86/platform
 # bad:  [d9e5f39a] Merge branch 'auto-oprofile-next' into auto-latest
 # bad:  [cbaff272] Merge branch 'auto-timers-next' into auto-latest

as the bisection comes up with that merge commit. Perhaps the 
combination of the x86/platform changes and the clocksource changes 
triggered it?

	Ingo